Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technique in which a user transmits on many orthogonal frequencies (or carriers). The orthogonal carriers are individually modulated and closely spaced, but do not interfere with one another. This provides high spectral efficiency and resistance to multipath effects. An orthogonal frequency division multiple access (OFDMA) system allows some carriers (or sub-carriers) to be assigned to different users, rather than to a single user. Today, OFDM transmission techniques are used in both wireline transmission systems and wireless transmission systems. OFDM and OFDMA techniques are also used for wireless digital audio and video broadcasting.
However, conventional OFDM/OFDMA networks do not fully and efficiently utilize the full bandwidth allocated or available to a base station in a wireless network. In particular, OFDM/OFDMA networks do not efficiently utilize the spacing between frequency channels in the available bandwidth of a given channel block.
Therefore, there is a need in the art for improved orthogonal frequency division multiplexing (OFDM) transmission systems and improved orthogonal frequency division multiple access (OFDM) transmission systems that allows efficient deployment of the system in spectrum blocks with various bandwidth.